The invention relates to a cyclone heat exchanger and, in particular, to a cyclone heat exchanger that serves as a preliminary stage of a dry process-type rotary kiln for burning cement clinker or the like, and that includes a plurality of heat exchange stages formed by cyclone separators arranged one above the other, an inlet for the delivery of raw meal to the heat exchanger, an outlet for delivering the heated raw meal from the heat exchanger to the rotary kiln, another inlet for delivering hot gas from the rotary kiln to the heat exchanger, and another outlet for delivering the cooled gas from the heat exchanger.
The cyclone heat exchangers of this type are well known and are widely used for saving energy during production of clinker in the dry process-type rotary kiln.
Usually, the raw meal which is supplied from a hot-air drying installation, is delivered to the inlet of the heat exchanger, passes through separate stages formed by the cyclone separators and, finally, is delivered from a heat exchanger outlet to the rotary kiln where the actual burning process in hot gas takes place. The raw meal passes through the rotary kiln and is converted into a clinker. At the rotary kiln end, the clinker is cooled down and is transported for further processing or storage.
The hot gas, which is used for burning the raw meal in the kiln, passes from the kiln and through the heat exchanger in a direction opposite to the direction in which the raw meal flows. After being preliminarily heated in a cooler at the kiln end, which serves for cooling the clinker, the heated gas flows through the kiln in a direction opposite to that of the raw meal.
After passing the kiln, the hot gas is blown by a blower through a gas inlet of the heat exchanger thereinto. In the heat exchanger, the still hot gas contacts the raw meal, which is delivered from the drying installation, in several stages. This results in heating of the raw meal and in cooling of the gas.
In each stage of the heat exchanger, the raw meal and the gas are again separated. The separation of the raw meal and the gas takes place in the cyclone separators. By tangential feeding of a raw meal gas mixture into a cyclone separator, centrifugal forces are generated in the separator. The centrifugal forces cause the separation of the raw meal and the gas. The raw meal slides along the funnel-shaped wall of the separator downward, whereas the gas moves through an immersion pipe upward.
To prevent densification, the raw meal is conducted to the below-located stage of the heat exchange through a down pipe. The gas is conducted to the above-located stage through a stand pipe. Because of the elevated temperatures of the raw meal, it is important that the raw meal passes from one stage to another through the down pipe.
As a result, the heat from the gas is transferred to the raw material in separate stages of the heat exchanger as the raw meal passes from the top of the heat exchanger downward. At that, the gas, which is delivered from the uppermost stage of the heat exchanger, e.g., to the hot air drying installation for drying the raw material, still has a temperature of about 300.degree. C. This significantly reduces the heating energy costs during the clinker production.
The above-described cyclone heat exchanger with a plurality of stages formed by the separators arranged one above the other is described in a publication "Cement-Lime-Gypsum" (Zement-Kalk-Gips", Bauverlag Wiesbaded, Issue 38 (1985), Book 2, p.p. 67-76.
Because of increasing energy prices, a trend has been observed in the latter years to increase the number of separate stages in the above-described cyclone heat exchanger for better utilization of the rotary kiln heat. If a conventional heat exchanger previously had four stages, in the latter years six-stage heat exchangers came into existence.
The height of a six-stage heat exchanger may reach 130 m and this, because of unproportionally rising constructional costs, leads to a sharp increase in investment costs for such a heat exchanger. Local conditions often prohibits construction of heat exchangers of such height, for example, the requirements of landshaft preservation or the necessity to insure the safety of low-level airplane flights.
Also, the requirements of maintaining and/or modernization of heat exchangers with additional stages and/or static problems make it often impossible to construct heat exchangers with additional stages.
Accordingly, an object of the invention is providing a cyclone heat exchanger having a reduced height in comparison with a conventional cyclone heat exchanger while insuring obtaining an adequate heat exchange capability.